**9. Conclusion**

The aim of the present study was to propose cetacean fibroblast cell cultures as an "in vitro" method, called "Test Tube Cetaceans", to investigate effects of environmental contaminants in these marine mammals. The data reported in this chapter confirm that the use of Test Tube Cetaceans is a good non destructive surrogate of "in vivo" cetacean test (killing) to evaluate the different hazards of cetaceans to pollution.

Regarding the toxicological susceptibility to some xenobiotic compounds and to PAHs, the main results showed that the basal level of CYP1A1 and CYP2B of different cetacean species is very dissimilar and this seems to be especially species-specific rather than related to the geographic range, diet, toxicological status, etc. in which the specimens were found. All pollutants, at different level depending on the species and of the dose of treatment, showed an inductive capacity of these cytochromes. At times the response was dose dependent, other was bell-shaped response and other was a discontinuous induction response.

The qualitative and quantitative MICA protein expression as toxicological stress marker of the immune system showed that the three species sampled in the Sea of Cortez (Bryde's whale, long-beaked common dolphin and killer whale) showed higher basal level of MICA in respect to all Mediterranean specimens, regardless of the species and the fact that they were sampled free-ranging or found stranded alive and then died. This sharp distinction between the activity of MICA found in the Sea of Cortez and Mediterranean Sea specimens is probably the most important result to be highlighted: it seems that the environment in which specimens live and, therefore, the anthropogenic stress to which they are subjected, are determinant in the response of this protein of the immune system. In the light of this result we can hazard the conclusion that the lower the anthropic stress of the specimens, the higher is the basal level of MICA.

The Comet assay proved to be a very useful tool for assessing the potential genotoxicity of PAHs in cetacean fibroblast cell cultures. Future investigations will be conducted to investigate the genotoxic effects of different classes of contaminants in striped dolphin and other cetacean species. This technique led to the evaluation of possible DNA damage in species never studied before in this field, in order to investigate the different susceptibility to various contaminants, using fibroblast cell cultures.

In conclusion, "Test Tube Cetaceans" can be proposed to the scientific community as the "in vitro" method used to replace the "scientific whaling" to study the toxicological threats of different species of cetaceans, primarily of endangered species such as fin whale and Mediterranean common dolphin, since the research priorities is the conservation for the maintenance of cetacean biodiversity.
